One method that weightlifters use to add resistance to a weightlifting routine is to utilize a stack of flat plates combined with either a low or a high pulley and a handle. The weightlifter pulls the handle and the handle is connected to a cable and the cable lifts as many of the plates as the weightlifter has selected. In this kind of weightlifting setup, the weightlifter can perform hundreds of different exercises using either the low or the high pulley in the same stack of weights to exercise virtually any muscle in the human body.
One way that weightlifters and other athletes increase the effectiveness of a workout is to find a way to do two exercises at once, or to exercise two muscle groups from the same position. An example of this is when a person stands or sits on a balance ball while performing some form of weightlifting such as dumbbell curls. Part of the athlete's energy and concentration goes into balance and core muscles and part goes into the specific exercise of using the dumbbells in a bicep curl.
Any weightlifting device which can incorporate two exercises into one position or one movement is thus a desirable improvement over previous devices.